Process for the vapor phase hydrogenation of olefin polymers



Dec. 26, 1 939. Q D Ruys Er AL 2,184,930

PROCESS FOR THE VAiOR PHASE HYDROGENATIQON 0F QLEFIN POLYMERS l File'd'Ilay 21. i955 2 Sheets-Sheet l Y [I4/afar@- 00a/anser J. D. RUYS ET ALLYMERs l PROCESS FOR THE VAPOR PHASE HYDROGENATION 0F OLEFIN PO FiledMay 21, 1935 2 sheets-sheet 2 40 method of operation in a plurality ofstages sensitive to depolymerization by heat which setsI Patented Dec.26, 1939 ,PATENT OFFICE PROCESS FOR THE VAPOR. PHSE HYDRO- GENATION 0FOLEFIN POLYMEBS Jan D. Ruys ana Ewald D. Pyzel, Pittsburg,-

Calif., assignors to Shell Development Company,`San Francisco, Calif., acorporation of Delaware Application MayNZl, 1935, Serial No. 22,570

2 Claims.

This invention relates to a novel method for the catalytichydrogenation` of olen polymers in the vapor phase wherebydepolymerization of the starting material may be substantially avoided,the life of the hydrogenation catalyst materially prolonged and thelosses of hydrogen greatly reduced while the thermal eiciency of thcprocess is also increased.

The vapor phase hydrogenation of polymeric bodies,-particularly olenpolymers, presents many diiculties. Not only are such compounds a verydefinite upper limit to the temperature which may be used, but also anequally definite lower limit of operating temperature is xed by thetendencyfof most 4suitable catalysts to be poisoned by small amounts ofimpurities whenused at low temperatures. The exothermic nature of thereaction makes it Very difficult to accurately control the reaction andmaintain a uniform temperature within the required limits. Furthermore,prior methodsr of hydrogenation have been found to be ineilicient in theuse of hydrogen', making them economically impractical for theconversionpf olen polymers to the corresponding saturated hydrocarbons.

We have now found, however, that by suitable adjustment of the operatingconditions ofthe reaction the difliculties of temperature control may besuccessfully overcome and not only mayv the vapor phase hydrogenation oiolefin polymers be carried out uniformly within a temperature range inwhich undesirable side reactions such as polymer decomposition and/orcatalyst poisoning may be` substantially suppressed but also in whichimportant thermal economies may be realized by utilizing the heat ofhydrogenation for vaporizing and/orpreheating the reactants. We havefurther found that all these advantages may be combined in acountercurrent-concurrent whereby very high hydrogen efficiencies may berealized while high conversions to saturated compounds -may also beobtained.

Our invention may be practiced with any suitable addition product orproducts of an olefin.

or its polymer and an unsaturated aliphatic' hydrocarbon, which may bevaporized without substantial decomposition, regardless of the sourceAor method oi preparation of such addition products. Suitable startingmaterials which may be advantageously hydrogenated by our process thusself (i. e., polymers) or with a diierent olefin or with otherunsaturated aliphatic hydrocar- (Cl. 26o-676) bons. The oleiin or olensused for the, preparation of the desired polymer or addition product maybe of any degree of reactivity, but our process is most especiallyadvantageous in its application to the hydrogenation of the abovedefined-.addition products of 'tertiary olens andv their polymers, areaction -particularly liable to involve decomposition when carriedoutinthe vapor phase. Thus, ethylene and/or secondary base olefms, i.e., iso and normal olefins which yield secondary derivatives such aspropylene, l-butene, 2-butene, l-pentene, Z-pentene,

base olefms, i. e., iso-olens, such as isobutylene, Z-methyl-l-butene, 2methyl 2 butene, etc., which yield tertiary derivatives, may be usedeither alone or in admixture with eachother or with other more reactiveunsaturated hydrocarbons such as acetylene and/or dioleiins, or withparains or other compounds which may be considered inert in thepolymerization and/or condensation process. The olen or oleiins usedmay' conveniently'be derived from mineraloils, as petroleum, shale oil,and the like, orfrom, mineral oil products, or natural gas, or4 coal,peat and like carboniferous natural materials-,as well as' fromvegetable oils, fats and waxes. The olens present in such startingmaterial may be of natural occurrence, the result of catalyticdehydrogenation, vapor or liquid phase cracking, or other A pyrogenetictreatment.'

Instead of the oleflns themselves, the corresponding alcohols, or otherderivatives, which yield the oleiins and/or polymerization productsthereof by suitable treatment, may be used as the source of the desiredpolymer or polymers.

Polymerization and/or condensation of the chosen olen or olefins may beeiiected in a number of different ways depending upon the product orproducts desired. Resort may be had, for i example, to lpressureheating, or to vtreatment with zinc chloride, boron fluoride, phosphoriction of linclude addition products of one olen with itand the like, andthen heating the resulting abmore reactive olein or olens present andthe' activity of the polymerizing agent used, that neg- 15, .ligibleconversion of the less reactive olefins occurs. Where alcohols are usedas starting material a similar procedure may be employed; In

either case this method of operation permits of accurate control of thepolymerization to yield olefin polymers of definite composition, forexample, polymers preponderantly' composed of dimers or trimers,'etc.,or mixtures of predictable proportions. f

However prepared, the olen polymers or addition products may be used inour process of vapor phase -hydrogenation in a pure state either as thechemical individuals or as pure mixtures or as the crude mixturescontaining paraflins or other compounds which are inert in the processor compounds which may undergo simultaneous hydrogenation or otherchange lunder the operating conditions used.

Any suitablehydrogenation 'catalyst tmay be used in our process.Activated nickel, iron, cobalt, metals oi the platinum group,particularly platinum and palladium, copper, chromium, manganese,titanium.' molybdenum, vanadium, tungsten and thorium are examples ofmetal catalysts Vwhich are particularly suitable, but otherhydrogenation catalysts may also be employed. The catalyst may be usedalone as an individual metal or a compound lthereof or as a mixture ofmetals, or a mixture of metals and compounds. vExam- I ples of mixedmetal catalysts include nickel-and molybdenum, nickel and chromium,nickel and manganese, etc., which may be prepared, vfor example, byreduction of nickel molybdate, nickel chromate, nickel manganate, andthe like. Mixtures of iron and nickel are preferably not used because'the activity Vof the mixture is usually less than that of nickel alone.Other -typical mixed catalysts are, for example, nickel and silica,nickel and boron o'xide, or the like, prepared, for example, byreduction of nickel silicate, nickel berate, etc., or nickel andalumina, prepared, for instance, by the reduction of a mixture of nickeland aluminum compounds. In the preparation of the `catalyst advantagemaybe taken of the promoter action of small amounts of diicultlyreducible oxides of heavy metals, or the like. Thoria, ceria, zirconiaand titania, for example, are particularly useful as promoters fornickel. The catalyst metal or mixture chosen may advantageously be usedin connection with an inert support such as pumice, infusorial earth,glass, porcelain, asbestos, charcoal', and the like, or on a Ametalsupport whereby the heat conductivity of thecatalyst mass may beimproved andcontrol of the catalyst temperature facilitated. Activemetal catalysts may be prepared by reduction of the corresponding oxide,hydroxide, carbonate, nitrate', carbonyl, or salt of an organic acidsuch as the formate, acetate', propionate, oleate, and the like. l l Inthe vapor phase hydrogenation of olen 'l polymers it is important thatthe temperature be maintained within a definite, and usually relativelynarrow, range. This is particularly true where the polymer or polymericmixture may contain small amounts of materials which `are poisons forthe more Idesirable hydrogenation catalysts, as is usually the case withpolymers derived from mineral oil sources which contain sulfur compoundswhich are very diiiicult to remove completely. We have found that thedanger of such poisoning may be greatly reduced, without resort toexpensive methods of treatment for the complete removal of impurities,by.

carrying out the hydrogenation above certain critical minimumtemperatures which vary with different catalysts. Thus, with nickel ornickelaluminum oxide catalysts, we have found that the life of thecatalyst may be very materially lengthened, in fact may be increasedmore than fifteen times by operating at temperatures of about 170 C. andhigher as compared with otherwise similar operations conducted at 150 C.and lower. A

Too high temperatures, on the other hand, are equally undesirable notonly because of the tendency of olefin polymers to depolymerize atelevated temperatures, but also because high temperatures also adverselyaffect the life of the catalyst. Highly active metal catalysts are bestprepared by low temperature reduction, and operations at temperaturessubstantially above the reduction temperature reduce the active life ofthe catalyst. The maximum temperature of operation will, therefore,depend both upon the particular polymer or olefinic addition productbeing hydrogenated and the nature and method of preparation of thecatalyst employed. The choice of operating temperature will'also begoverned by the degree of saturation desired in the iinal product, thespace velocity which is used, the pressureconditions of4 operation andthe practicality of' using inert gases to assist in the control of thereaction temperature. Thus, when it is desired to employ high spacevelocities at the sacriflce of complete conversion of the polymer tosaturatedhydrocarbons, higher temperatures may Vbe used than areadvisable where substantially completely saturated end products are tobe produced. When substantially completehydrogenation of the polymer isdesired, the time of contact generally required is such thattemperatures above about 350 C. can seldom be used without danger ofexcessive depolymerization. We prefer, therefore, to operate Within atemperature range of about 170 C. to about 350 C. When it is desired toemploy high space velocities, it may be of advantage to operate attemperatures near the upper limit of the allowable range. If low spacevelocities are employed it is more desirable to operate at temperatures'near the lower limit of the range. The term space velocity may bedefined as -the volume of olen polymer flowing through the apparatus perunit of time,

. per unit volume of hydrogenation catalyst under standard conditions oftemperature and pressure.

In general, we prefer to employ temperatures as low aspossible,'consistent with practicable rates of throughput, as control ofthe temperature is facilitated thereby.

'Ihe particular catalyst, or catalyst mixture chosen may influence thechoice of operating temperature not only by its eiect upon the rate ofhydrogenation but also by its eiiect upon side reactions. In view of thevarious factors involved, we preferably employ in operations at aboutone to two atmospheres absolute pressure with nickel catalystscontaining little or no materials of highly active dehydrogenatingproperties, a. temperature range of about 170 C. to about 275 C., forthe hydrogenation of di-isobutylene at space velocities of about 0.2 toabout 2 volumes per hour per volume of catalyst. With nickel catalystscontaining substantial amounts of dehydrogenating agents such as chromicoxide. etc., on the other hand, we prefer to operate in a temperaturerange of about'l'lO" C. to about 220 C. under otherwise comparableconditions. With polymers having lower hydrogenation rates, such astri-isobutylene, and with mixed catalysts of the type of 'Ni-A1203,etc., for further example, a temperature range of about 225 C. to about275 C. at space velocities of about 0.05to about 0.5 volume per hour pervolume of catalyst', is

preferred. Y

Either atmospheric, superatmospheric, or subatmospheric pressures maybeused. Subatmospheric pressures are most advantageous whenhydrogenating very highly polymeri'zed olefins which have a tendency todecompose at theirvnormal boiling point.- Superatmospheric pressurestendto increase the rate of the hydrogenation reaction. The hydrogenationrate of triisobutylene, for example, isabout 25% faster at apressure ofvaboutl 115 lbs. per sq. in. than at 35 lbs. per sg'. in. -We preferablyavoid excessively high pressures, however, as the cost of equipment isgreatly increased thereby.

Inert gases may be introduced withV the reactants to facilitateltemperature control and assist in preventing secondary reactions,particularly decomposition reactions. For s uclrpurposes` any gas orvapor which is inert under the con.

ditions of the reaction may be used, such, lfor .l example, as\nitrogen, or a highly stable hydrocarbon such as methane, or the like.Alternative- 40 ly an excess of one of the reactants, i. e., an

excess of either hydrogen or oleiinpolymer or recirculation of apart ofthe product may. beM used for the same purpose.

In lieu of, or in addition to, the use of inert diluent gases forabsorbing the heat lliberated by the reaction, an inert substance ofsuitable constant boiling point may -beintroduced with the reactants, orthe reaction zone may be surrounded by a selectedconstant boilingsubstance which on vaporization absorbs the liberated heat and therebymaintains a substantially constant J temperature.j Non-boiling baths maybe similarly used by providing means fcr cooling. and, recirculating theliquid bath medium.- Such cooling may be' eected in air and/or'watercooled spray towers, or tubular heat exchangers, or'the like. yMoreadvantageously, the heat imparted to the bath lby the reaction may beremoved by circulating hydrogen and/or the olefin polymer to be 0hydrogenated through heatexchange elements in heat exchange relationwith the bath uid.

Suitable media which may be used as the bath l v rated product isobtained which can not be sepa- `.rated into its Acomponents by simplefractiona.-'

.uid' include high-boiling organic compounds of which petroleumfractions such-as lubricating o il fractions and the like,diphenyLpolyalkylated naphthalenes, as di-secondary butyl naphthalene,and the like, are typical, and inorganic materials, such as mercury,leadand like low-melting metals, or metal mixtures such as a 30-70lead--- tin mixture forexa'mple, or low-melting alloys, as

Woods metal, bismuth solder, etc.,'or fused salts as, for example, aeutectic mixture of sodium` nitrate and sodium nitrite, or the like.Such baths preferably surround the catalyst tube or tubes in" such amanner that uniform cooling is ais- 1,980

fbe used to preheat the .olefln--polymer'to be hydrogenated, -Theheating in this-case 'being eff ed b y airand/orjwater cooling ortlielike and the peratures in all parts of -the system is facilitated.

may be facilitated, lwhen a plurality of catalyst tubes are used, byarranging the tubes more compactlynear. the periphery of the bath, wherelower bath temperatures usuallyl exist as al re'- Vsult of cooling bythesurrounding atmosphere,A

The'heat o freaction absorbed'bythe bath-may beremovedfandadvantageously utilized by circulating the. heated mediumheatexchange relation with the hydrogento be'used-injtlie re` action. j vThehydrogen thus preheated may lthen fected by direct contact.f orexample.` Where exy cess heat above `that required for vapo'rizi ng thepolymer and/or preheating the 4reaction mixture' is to beremoved, thecooling may be supplementheatedair or water so obtained may be disposedof in any suitable way either'being permitted to escapeto waste or beingused as a source of heat for some `other process carried on in proximityto the hydrogenation unit. Instead of-usingf-thehydrogen as theprincipal medium forcoolingthe temperature regulating bath thezpolymer-to be hydrogenated may be so "user l. l Since olen polymers aresensitive to over heating, however, it may be more advantageous to usethe reaction mixture of both olefin polymer and hydrogen as the bathcoolingmedium, as the presence ofthe y hydrogen serves to protect thepolymer from excessive heating.

In certain cases, especially where the apparatus isnot well insulatedand heat losses are high, the heat required for vaporizing thepolymerand preheating the reaction mixture'to the desired temf perature may besuch' as to reduce the temperature of the cooling bath below the optimumfor recirculation to the reaction system.` Such con dition may berectied by partlyprehea'ting the reactants before bringing them intoheat exchanging relationship with the 'bath medium or supplying the bathwith heat from an external source before such exchange. Morepreferably,v however, the extra heat is added to the system byre-heating the bath medium just prior to its return .to thehydrogenation unit' as by this method of operation control of operating,tem- The use of one of the reactants in excess to function as aninertdiluent to assist in the control of the reaction temperature has alreadybeen mentioned. In single stage operations thisv has so'medisadvantages." For example, if the olefin. polymer is used in excess anincompletely 'satuhydrogen may seriously interfere withits corrj We havefound that these difculties may be-entirely avoided by carrying outtinued re-'use.

the hydrogenation inl a pluralityof stages whereby'all the advantageskof countercurrent. cpera-.

tion. may be obtained. Thus, insa `two-stage op-Y 75 promoted throughoutthe catalyst zone.` This l prolonged heating gradually renderreactivationeration, for example, the rst stage of hydrogenation may becarried out in the presence of an excess of polymer using the hydrogencontaining I gas remaining from the second stage of hydrogenation inwhich second stage an excess of hydrogen is present over that requiredfor reaction with the partly converted polymer from the first stage. Itwill be understood that this aspect of our invention is not restrictedto olefin polymer hydrogenation alone but may be advantageously employedwith anyhydrogenatable material, including unpolymerized olefins,aromatic compounds, unsaturated alcohols, and the like.

Our process may be carried out as a batch, intermittent or continuouslmode of operation.

Any suitable'source of hydrogen may be used for the process. Thehydrogen `need not be substantially pure since the presence of inertdiluents is not detrimental. Suitably purified coke oven gas, oil gas,and the like, or gases obtained by the dissociation oi' ammonia. orbythe dehydrogenation of alcohols etc., may be used as the source ofhydrogen for our process. The use of gases of very low hydrogen contentmay, how,- ever, materially reduce the rate of reaction and consequentlythe capacity of the apparatus. Substantial amounts of oxygen compounds,such, for example, as carbon monoxide and/or water vapor in thehydrogen-containing gases are preferably avoided where nickel-containingcatalysts are used, as temporary catalyst 'poisoning may resulttherefrom. Catalysts so poisoned may, however, be readily reactivated,by the use of hydrogen substantially free of these materials.

The same general method of precedure may be used to greatly prolongtheactive life of any catalyst used in vapor phase hydrogenation,whether the cause of its poisoning is due to impurities in thehydrogenatable material used, or in the hydrogen containing gas, orboth. By operating with -a reaction mixture containing a concentrationof catalyst poisons above the critical (i. e., the concentration atwhich an impurity begins to adversely aiect the activity of a catalystunder the conditions of the reaction) for a part of the time, until theactivity of the.

catalyst falls below a predetermined value, and then replacing eitherone or both of the impure reactants, as required, by material ofcatalyst poison content belowV the critical, the activity of thecatalyst may be substantially increased and in most cases brought backto the same value which the catalyst would have had if poisonv free.reactants. had been used thruout. The lesspure reactant or reactants maythen be again introduced and the cycle repeated as many times asnecessary to maintain the desired average activity, until therstructuralchanges accompanying increasingly diiiicult and the application of moredrastic methods, suchl as the formation of a salt' of the metal involvedfollowed by reduction thereof, becomes advisable. By this cyclic methodof operation important savings in puricationgcosts may be realized sinceonly a fraction ofthe total material reacted `need be treated. Forexample,

by-product hydrogen from the conversion of alcoliols4 to ketones may be-used to replace 90% of the hydrogen -used for hydrogenation of di--isobutylene without reducing the yield oi isoabout 0.01% sulfur contentor less, with similar saving.

' The effluent vapors from the raction unit or units may be condensedand any gases present therewith separated, in any convenient manner. Bypassing the polymer to be hydrogenated, with or without hydrogen, inheat exchange relation to such etlluent vapors further heat economiesmay be eiected. I l

For the purpose of aiording a clear understanding of our invention itwill be described with more particular reference to the hydrogenation ofthe dimers and trimersof isobutylene, but it will be understood that `weare not to be limited thereto as the principles involved are applicableto the hydrogenation of a wide variety of other olefin polymers andaddition products. The application of our invention to the hydrogenationof isobutylene polymers may be best explained by reference to theaccompanying drawbe used as an example-is mixed with hydrogen orhydrogen-containing gas, in this case pure commercial'hydrogen, in thefeed inlet pipe I.'

The hydrogen is preferably used in slight excess, for example, about 1.1to about 1.5 mois of hydrogen per mol of tri-isobutylene. 'I'he mixtureof liquid tri-isobutylene and gaseous hydrogen is forced through aheating coil 2 surrounded by a heated bath 3 containing hot oil from theconverteras will be more fullydescribed hereinafter. Here thetri-isobutylene is vaporized in the lower submerged coils and'the mixedvapors are preheated to the required reaction tempera,- ture in theupper exposed coils by the hot oil spray I1. The hot vapors oftri-isobutylene and hydrogen are then conducted via line 5 to aconverter 6 where the preheated reaction mixture passes through aplurality of catalyst tubes l surrounded by a circulating oil bath 8.The catalyst used in the present case was prepared by saturatingporcelain with a solution containing nickel nitrate and aluminumchloride and iirst roast- -ing and then heating the impregnatedporcelain pipe I2 and returned to the hydrogen supply (not octane perpound of catalystV below that obtainn able when pure commercial hydrogenis used exclusively. Also, for further example, di-isobutylene ofrelatively high sulfur content may be intermittently replaced bycli-isobutylene of shown) for reuse. Where the excess hydrogen separatedin separator II is very small and/or where it is mixed withrelatively'large amounts of inert gases it may be more economical tovent the separated gas to the atmosphere through Valved vent I3 than toattempt to reuse it. Vent genated-substantially pure tri-isobutylenewill 225 C. to about 240 C. The oil is Withdrawn4 I3 may also be used tointermittently eliminate accumulated impurities in the hydrogen when thelatter is being recycled. The hydrogenated product containing from aboutto 99+% isododecane, under the above conditions during the normal lifeof the catalysts, is withdrawn through drain I4 to storage.

The temperature of the hydrogenation is regulated by an oil bath 8surrounding and in heat exchanging relationwith the catalyst tubes orzones 1, already mentioned. 'I'his bath is continually supplied with oilat about 200 C.240 C. which circulates around the catalyst tubes 1 at arate suflicient to maintain the reaction zone at a uniform desirabletemperature. Under the conditions of one typical run, the temperature ofthe vaporied, hydrogenated product-was about through pipe I6 andconducted to the evaporator l where the hot oil is sprayed over theexposed coils of the heat transfer element 2 to preheat the vaporizedreactionmixture therein and 'is then collected around the lower coils ofthe vaporizing tube wherein, the tri-isobutylene is vaporized and nallywithdrawn, much cooled,` through pipe line I8 and pumped by pump I9 andline 20 tof furnace 2l or cooler 22 wherein the temperature of the oilis adjusted to the proper value, and returned to bath 8 for a repetitionof the cycle. By this method of operation, not only may high conversionsbe obtained at high rates' of throughput but also long catalyst life maybe obtained.

In the modification of our invention illustrated by Figure II,substantially pure di-isobutylene, for example, is fed from storage tankI by pump 2 and pipe line 3 to a primary ,vaporizer l. Before .enteringthe -vaporiaer 4, hydrogen-containing gas. from the secondary converteras will be described in greater detail later, is admixed with thedi-isobutylene. eThis gas may be oftrelatively low hydrogen contentbecause complete conversion of di-isobutylene to iso-octane in the rst`converter is not contemplated. In the primary vaporizer I thedi-isobutylene is vaporized and tbe mixture of di-isobutylene vapor andhydrogen-containing `gas is preheated by hot circulatim; oil. Themixture of gaseous reactants then passes by pipe line 5 to the primaryconverter 6 which may be of the same type as that described inconnection with Figure I. With the large excess ofpolymer present, thehydrogen is substan Helly completely reacted' but the conversion ofdi-isobutylene is relatively low. 'I'he reacted .mixture leaves theconverter .in vapory form 'through -pipe 1 and is condensed in condenser8 and flows to separator 9 where any'gas'es present are vented to theatmosphere through valved line In. \Such gases will be largely the inertconstituents of the hydrogen-containing gas originally used since thehydrogen will have been practically consumed. The partly converteddiisobutylene is pumped by pump. I2 through lines Il and I3 to thesecondaryvaporizer I1. Hydroeen nr hydrogencontaining' gas'. forexample, a mixture of '75% hydrogenand 25% nitrogen such asis obtainedby dissociation of ammonia, is added by pipe line I5 from pump'IG, tothe par-4 tiallv converted polymer preferably in about 'thestoichiometric 'proportion for reaction with the original unconverteddi-isobutylene feed to the primary converter 6 or a very smallexcessthereover, for example, -1 to 2% excess. Larger ex cesses of hydrogenmay, of course, be used but little advantage is gained thereby and thehy- ,stoichiometric requirement for reaction with half the incomingdi-isobutylene in line'3. The redrogen losses are materially increasedunless provision is made for recovery of such excess from the wastegases discharged at III. So in the preferred method ofconcurrent-countercurrent operation, the hydrogen fed rto the converterin which the final hydrogenation is effected is equivalent to the,polymer feed to the primary converter, and therefore represents asubstantial excess of hydrogen over that required for hydro- .genationof the unreacted polymer`l present in the iinal converter. Thisunreacted excess of hydrogen serves, at least in part, as the hydrogencontaining gasjused to effect the initial partial hydrogenation of thepolymer.

Many advantages may be obtained by careful adjustment of the operatingload on the converters'so that each performs an equal share. In this waynot only may the average life of the catalyst in the converters beprolonged, but alsot thecontrol of -the .operating temperature is 20greatly facilitated since approximately the same amount of heat will begenerated in each unit. Balanced operation-.of the two converters shown.in Figure II may lbe facilitated by the introduc-` tion of additional,fresh, hydrogen-containing gas to the primary converter via valved lineIl and the regular hydrogen feed line 25. In order to insurebalancedoperation, the addition in this way of a slight excess ofhydrogen above the of the polymer material present in the primaryconverter may be -justified under some conditions in spite of thehydrogen losses which may result therefrom. In some cases less`thanstoichiometric amounts of hydrogen calculated on the polymer feed to theprimary converter may be added in the secondary converter and theremainder and/or any desired excess may be fed directly to the primaryhydrogenating lmit as by line Il. An important feature of this widely\applicable step of our procedure is the presence in the firsthydrogenation stageofaesubstantial stoichiometric excess ofhydrogenatable compound over hydrogen, while the reverse relationship ismaintained in the last hydrogenation stage. In two stage operationsfmost preferably the feed to the primary converter is hydrogenat ablecompound and hydrogen in a molecular/ ratio of about two to one, and thefeed to the secondaryconverter is these reactants in the ratio of aboutone to two.

In the secondary vaporizer I1, the partly con V`rted di-isobutylene isagain vaporized and preheated as described for the primary vaporizer-l.'I'he reaction mixture, at substantially reaction temperature, is then'conducted by-pipe line I 8 tothe secondary converter I9 where, due tothe presence of an excess of hydrogen the conversion of di-isobutyleneto isooctane may be made very complete. The reaction product passes .outthrough pipe line 20 to condenser 2Iand sepa-l rator 22. Iso-octane isdrawn of! through pipe lin'e 23' and the unreacted hydrogen and admixednitrogen is sent'by pipe line 2 5 to be mixed with action temperaturesin converters 6 and I9 may be controlled, and the polymer vaporizationeifected, in the same manner as described in c onnection with .Figure I.A somewhat'more flexible system 'which accomplishes'the same result isshown, however, in Figure II. In this case a suitable oil such as usedlubricating oil or theMA like. is circulated by pump -26 through pipeline 21 toa cooling device 28 and/or a heater 23.

After suitable adjustment of the oil temperature 'if auf and/or 3|`tothevalved branch lines 32 and 33. By proper manipulation of the valvesin these branch lines the temperature of the oil entering the converterbath at 34 lmay be varied over a very wide range. After circulating inheat translferring relationship with the catalyst zones of,

3| is' also withdrawn through valved brancl'ipipeV line 39 to eectpreheating of the reaction mixture and vaporization of the partlyconverted diisobutylene in the secondary vaporizer The oil issubstantially cooled in these operations and passes out by line 40 tojoin pipe line- 4| for return to pump 26 and a repetition of the cycle.A similar system of reaction temperature control and preheating andvaporization is used in the primary stage. Corresponding elements in theoil circulation system of the primary converter and vaporizer aredesignated in Figure 2 by members' ten higher than the same elements inthe.' secondary system above described.

It willbe evident that this method of temperature control permits ofvery accurate control with' great heat economy. Not only may thetemperature of the oil leaving -the cooler and/or heater be variedwidely and either of these elements be completely shut off from thesystem but also further modification of the oil temperature in theconverters maybe effected by controlling' the relative amount of oilrecirculated by pumps 31 and 41 as compared with the total oil input at34 and 44. At the same time vaporization and preheating of the reactionmixtures are eifected essentially by the heat of reaction absorbed incontrolling the temperaturepf Vthe converters. l'

When operatingby the above described concurrent-countercurrentprocedure, either the same, or diiferent hydrogenation catalysts may beused in the converters or hydrogenation catalyst zones. Under someconditions it may, for example, be advantageous to have catalysts ofdiierent susceptibilities to poisoning and/or different reactivitiespresent in the different converters. In such cases the temperature ofoperation and/or other conditions may be varied in the differentconverters to meet the 'requirements of the different catalysts.Furthermore, whether operating with the same catalyst in each zone ornot, it may sometimes be desirable to alter the order of operation anduse the converter in Which the primary hydrogenation has been effectedtoc/carry out the secondary stage of hydro genation and vice versa."Thus in the arrangement shown in Figure II the di-isobutylene feedmaybe pumped by kby-pass line connecting 'with line 3 feeding tovaporizer Il and the primary hydrogenation-effected in converter I9 bymeans of hydrogen supplied by line 52, the partially hydrogenatedproduct being condensed and gases separated as before. Non-reactivegases maybe vented via line 53 while the partially lhydrogenated polymeris fed by line 54 to pump l2 and thence by lines I3, 55 and 3 tovaporizer 4 with hydrogen-containing gas supplied from lines I4 and 25.The final product during such a reversed cycle is withdrawn byline 5E.This ment to the previously described cyclic procedure 2,184,930 inthese devices, the oil passes by pipe lines 30- using reactants ofdifferent purities, and may in some cases of purely temporary catalystpoisoning entirely obviate it. The same principle may be applied whenonly one hydrogenation catalyst chamber ,is used. dThus in the method ofoperation illustrated by Figure I, for example, with impure reactantsintroduced k thru pipe line 5, thev activity of the catalyst at theupper end of the converter Will be most noticeably affected and thereacted product leaving via line 9 will be essentially freer of thoseimpurities which were responsible for this loss in catalyst activity.After the catalyst activity in the upper end of converter 6 has fallento a predetermined rate, the ow of reactants may be reversed bymeans ofvalved by-pass lines 23 so that the reactants are introduced thru line 9and the reacted mixture withdrawn thru a part of line 5 by a bypass line24 connecting with line 9. The activity of the catalyst in the lowerpart of the converter will now gradually decline if catalyst poisons arepresent in the reactants but the activity of that partv of the catalystmass at the top (now the exit) will be gradually restored due to thepre'sence of relatively poison free reactants in that zone. The impuritycontent of the product will then approximate that of the feed until theactivity of the catalyst at the lower end of the converter has declinedto the point where another reversal of ow is desirable.

The foregoing illustrative examples are not to virtue of any detailtherein specified-as various permissible deviations therefrom will beevident to those skilled in the art of hydrogenation. For example,various changes may be made in the arrangement of apparatus, such asplacing the olefin polymer vaporizing coils within the hydrogenationunit or units either to function there as a cooler for the bath mediumor to take the place in part or in whole of the bath uid itself.Furthermore, while' emphasis has been placed upon the more advantageouscontinuous methods of operation, substantially the same ultimate-results maybe had by intermittent or batch methods of operation, asWhere, for example, the process illustrated .by Figure II is carried outusing only one catalytic converter and storing the various reactantsbetween the various operating stages.' Furthermore, while theconcurrentcountercurrent method of procedure has been specificallydescribed in connection with a twostage process, it will be apparentthat a larger of the material undergoing hydrogenation isy eected beused, for the sake of greatest economy,

. in an earlier hydrogenation stage. lThat is, irrespective of thenumber of hydrogenation steps, it isadvantageous to eiect. a separationof unreacted gases after each and to carry out the final or completionof the hydrogenation with fresh hydrogen containinggas. Preferablyhydrogen separated from thereacted mixture of a preceding hydrogenationcatalyst zone (i. e., a zone in which the hydrogenation of thehydrogenatable compound is more complete) will be present in all thehydrogenation zones except the nal zone. Most preferably thehydrogen'thus added in a plurality of hydrogenation zones will representin total, as has already been emphasized, approxmately thestoichiometric requirement for reaction with the original hydrogenatablecompound or material used.

As has been indicated. a wide variety oi olen polymers. and condensationproducts or oiens may be successfully hydrogenated by the above or othermodifications of our invention by proper adjustment ot the 'operatingconditions. Not only may other tertiary oleiin polymers, such as di andtri amylenes and hexylenes and the m like, be thus treated, but alsopolymers oi less reactive oleilns and 4olefin condensation productssuch, for example, as the iso-nonenes produced by interaction 'ofisobutylene with tertiary amylenes, or isohepiylene which may beobtained by reaction of iso-butylene with propylene, etc.,

or octylenes obtained by the reaction of secondary butylene with atertiary butylene may be similarly hydrogenated, as well as likeproducts oi higher homologues and analoguesv .and higher pOlymerizationand] or condensation products.

Our process offers many advantages. It is particularly useful for theconversion of unstable gum forming olene polymers and/or condensationproducts into stable saturated hydrocarbons oi g5' high anti-knock'valueeminently suitable for use as motor fuel and the like. These valuableproducts may be prepared by our method at very high eiiiciency of bothheat and reactants.

While we have in the' foregoing described in understood that this-isonly for the purpose of making the invention more clear and thaty theinvention is not io be regarded as limited to the 35, 'details ofoperation described, nor is it dependent upon the soundness or accuracyof the theories advanced as tothe advantageous results attained. 0n theother hand, the invention is'to be regarded as limited only by the termsoi the accompanying 4i) claims in which it is our intention'to claim allnovelty inherent therein as broadly as is possible in view of the priorart.

We claim as our invention:

1. In a continuous process lfor effecting the 45 vapor phasehydrogenation of an unsaturated hydrocarbon to the correspondingsaturated compound in the presence oi an active hydrogenation catalystwhen the unsaturated hydrocarbon to be hydrogenated contains more than acritical conlo' centration oi a catalyst poisoning impurity whichpoisons the catalyst by forming a loose association therewith, the stepswhich comprise passing the vapors or the unsaturated hydrocarbon,together with an eilective amount of tree hydrogen, in one y directionthrough a mass oi the catalyst under f hydrogenation conditions andcontinuing the hydrogenation until the activity oi-the catalyst hasdecreased to a predetermined minimum practical arenoso .7

value due to temporary poisoning vof that part oi' the catalyst masswhich rst comes into contact. with the material to be hydrogenated, thenreversing the ilow of the unsaturated material and hydrogen and passingit in the opposite direction 5 through the same catalyst massunderhydrogenavtion conditions so that it ilrst contacts that portion ofthe catalyst mass which still has substantially its initial activity andcontinuing the hydrogenation until the 'activity of the catalyst hasIl)v decreased to a predetermined minimum practical value, then againreversing the iiow and continuing the cycle as described whereby the endof the catalyst mass which iirst contacts, the material to behydrogenated progressively loses activity while 15 the opposite end* ofthe same catalyst mass is being reactivated while substantially completehydrogenation of the unsaturated hydrocarbon is being eilected, and theactivity of the catalyst is maintained within a practical operatingrange.

2. In a multi-stage continuous process for effecting the vapor phasehydrogenation oi an unsaturated hydrocarbon compound to thecorresponding saturated hydrocarbon' in the presence of an activehydrogenation catalyst when the unsaturated hydrocarbon to behydrogenated contains more than a critical concentration of a catalystpoisoning impurity which poisons the catalyst by forming a looseassociation therewith, the Vsteps which comprise passing the vapors ofthe unsaturated organic hydrocarbon, together vwith an effective amountoi free hydrogen, successively through a plurality of hydrogenationstages containing a hydrogenation catalyst under hydrogenationconditions and continuing the hydrogenation until the activityof thecatalyst in the rstlof the seriesuofwhydrosenation .stages has decreasedto a predete A ed minimum practical value due to poisoning, thenchanging the order of the hydrogenation stages so that the original sec-4i)l ond becomes the rst stage and the original rst stage becomes thenal stage and continuing the hydrogenation until the activity of the`catalyst in the original second stage has decreased to a predeterminedminimum practical value due to 46 poisoning and continuing the cycle asdescribed whereby the catalyst in the `iirst ci the series oihydrogenation stages progressively loses activity while the catalyst intheflast of the series oi hydrogenation stages is being reactivated andVlili while substantially complete hydrogenation oi the unsaturatedhydrocarbon is being effected and the out-put of the system is keptsubstantially constant by maintaining the activity lof the catalystwithin a practical operating range. u Y

JAND. Roys.

swam D. Pimm.

